which are injurious to vegetation. 227 



detected the same insects in blasted limbs, and his discoveries have been 

 confirmed by Mr. Henry Wheeler and the late Dr. Oliver Fiske, of Wor- 

 cester. Mr. Lowell submitted the limb and the insect contained therein 

 to the examination of Professor Peck, who gave an account and figure of 

 the latter, in the fourth volume of the ' Massachusetts Agricultural 

 Repository and Journal.' From this account, and from the subsequent 

 communication by Mr. Lowell, in the fifth volume of the ' New England 

 Farmer,' it appears that the grub or larva of the insect eats its way in- 

 ward through the alburnum or sap-wood into the hardest part of the wood, 

 beginning at the root of a bud, behind which probably the e^^ was depos- 

 ited, following the course of the eye of the bud towards the pith, around 

 which it passes, and part of which it also consumes ; thus forming, after 

 penetrating through the alburnum, a circular burrow or passage in the 

 heart-wood, contiguous to the pith which it surrounds. By this means 

 the central vessels, or those which convey the ascending sap, are divided, 

 and the circulation is cut off. This takes place when the increasing heat 

 of the atmosphere, producing a greater transpiration from the leaves, ren- 

 ders a large and continued flow of sap necessary to supply the evapora- 

 tion. For the want of this, or from some other unexplained cause, the 

 whole of the limb above the seat of the insect's operations suddenly with- 

 ers, and perishes during the intense heat of midsummer. The larva is 

 changed to a pupa, and subsequently to a little beetle, in the bottom of its 

 burrow, makes its escape from the tree in the latter part of June, or begin- 

 ning of July, and probably deposits its eggs before August has passed. 

 This little beetle, which is only one tenth of an inch in length, was named 

 Scolytus Pyri, the pear-tree Scolytus, by Professor Peck ; it is of a deep 

 brown color, with the antennae and legs rather paler, or of the color of 

 iron-rust. The thorax is short, very convex, rounded and rough before ; 

 the wing-covers are minutely punctured in rows, and slope off very sud- 

 denly and obliquely behind ; the shanks are widened and flattened towards 

 the end, beset with a few little teeth externally, and end with a short 

 hook ; and the joints of the feet are slender and entire. It is evident that 

 this insect cannot be retained in the genus Scolytus, as defined by modern 

 naturalists ; but the condition of my specimens will not enable me to deter- 

 mine with certainty to which of the modern genera they are to be referred. 

 The minuteness of the insect, the difficulty attending the discovery of the 

 precise seat of its operations before it has left the tree, and the small size 

 of the aperture through which it makes its escape from the limb, are pro- 

 bably the reasons why it has eluded the researches of those persons who 

 disbelieve in its existence as the cause of the blasting of the limbs of the 

 pear-tree. It is to be sought for at or near the lowest part of the diseased 

 limbs, and in the immediate vicinity of the buds situated about that part. 

 The remedy, suggested by Mr. Lowell and Professor Peck, to prevent 

 other limbs and trees from being subsequently attacked in the same way, 

 consists in cutting off" the blasted limb below the seat of injury, and 

 burning it before the perfect insect has made its escape. It will therefore 

 be necessary, carefully to examine our pear-trees daily, during the month 

 of June, and watch for the first indication of disease, or the remedy may 

 be applied too late to prevent the dispersion of the insects among other 

 trees." 



The injury to which our wooden houses is subject from 

 the gallery mining operations of the Callidium bajulus, is 



